A new study from a Washington, D.C.-based advocacy group takes a look at the near-term costs of projected sea level rise due to climate change. Washington faces the highest cost on the West Coast for impacts to shorelines.

The study, "High Tide Tax," released Thursday by the Center for Climate Integrity, is meant to be a registry of the bare minimum states will have to spend to defend themselves against sea level rise. The authors wanted to create a consistent measure that could be compared across all states. So, they looked at the cost of installing seawalls or bulkheads to protect infrastructure that would otherwise be inundated two decades from now.

“The numbers in here actually give you an idea of what the real cost would be, conservatively, to a community,” said lead author Paul Chinowski, an engineer and director of the environmental design program at the University of Colorado, Boulder.

In the report, the tally for Washington state, with its long coastline and many coastline communities, comes in at $24 billion dollars.

The researchers looked at 150-meter square grids on a high-resolution map of the entire U.S. tidal and coastal shoreline, from Maine to Washington state. If 15 percent of the area of any one of those grids is flooded by 2040 — under a scenario for modest sea level rise and looking at the kinds of floods that typically happen once per year — the authors concluded that a barrier would need to be built to protect it.

The total for Washington added up to 1,651 miles of seawalls or bulkheads. Total cost was calculated as an engineering design firm would, looking at cost per mile of infrastructure to be built. Cities facing the highest expense — as detailed in the report — include Seattle ($716.3 million), Camano ($580.7 million), Ocean Shores ($393 million) and Tacoma ($382.3 million).

“We’re actually talking about things that have to be built within the next decade, to try and offset these impacts that are anticipated by 2040,” Chinowski said, adding that there are likely many other options besides seawalls and bulkheads that would need to be considered, knowing that the effects on wildlife, for example, must be taken into account. But the authors believe those options would typically be more expensive.

Washington officials are still looking at the data and methods used in the report, but they say they are taking action to make communities here more resilient and prepare for the unavoidable effects of sea level rise.

Ian Miller, a Coastal Hazard Specialist with Washington Sea Grant was the lead author on a sea level rise assessment tool released by the Washington Coastal Resilience Project, published last summer. He says when he looked at the cost cited for Port Townsend, where he lives, his initial gut reaction was that it was too high, at $283.3 million. He says he's still analyzing the data used and the methodology in the report.

“But, certainly what this study says — and this is not a surprise — is that defending our communities against sea level rise will definitely cost money. And it will cost Washington state a lot of money, because we do have such a long coastline and we have a lot of coastal communities,” Miller said.

He added that, unlike other side effects of a warmer climate, sea level rise is not something that cutting carbon emissions now will have much effect on. Higher tides are already “baked in” to scenarios for the near-term future. For that reason, he praised the near-term focus of this report.

The report shows East Coast states with the highest costs in 2040. The top three are Florida, Louisiana and North Carolina. Washington’s cost is the seventh highest in the nation. On the West Coast, Oregon comes in 16th and California eighth.

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